Organic Extracts: Potential for Fertilization and ... · PDF fileOrganic Extracts: Potential...
Transcript of Organic Extracts: Potential for Fertilization and ... · PDF fileOrganic Extracts: Potential...
Water control Mineral
control
Tomato leaves 50g
DM l -1
Cabbage50g DM l-1
Tomato leaves 100g
DM l -1
Cabbage 100g DM l-1
Experimental trials in Italy Qualitative Research in Cambodia
�To study the dynamics of N mineralization and release during extraction process, with different plant materials
�To test the fertilizing value of liquid extracts used as fertigation on a crop
�To understand the relevance of organic extracts for vegetable fertilization in developing countries
�To collect information on preparation and use of organic extracts for fertilization in a country where the technique is used
How is the use of organic extracts a
relevant and potential N resource for
small-scale vegetable fertilization in
tropical countries and how are they
currently produced and used?
Organic Extracts: Potential for Fertilization and Relevance of Use in
Tropical CountriesElena Gioseffi1, Bino Leonardi2, Francesco Giuffrida2 and Andreas de Neergaard1
1 Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen, Denmark2 Department of Horticulture & Food Technology, University of Catania, Italy
Vegetable production can play an important role in improving livelihoods of resource-poor farmers in tropical countries. In vegetable fertilization, nitrogen (N) is one of the most important nutrients. However, chemical N fertilizers are becoming more expensive and often out of reach for smallholders, and common organic fertilizers have a slow nutrient release compared to these. Therefore, farmers need a quick-acting and cheap N fertilizer suitable for vegetable production. Organic extracts are widely used in many tropical countries as top-dressing fertilizer, but few scientific studies have been made to understand their effectiveness.
Background
Objectives
Summary of findings
Results
Methodology
�3-week extraction experiment in water using crop residues:• Cabbage leaves (Brassica
oleracea var.botritis)• Tomato leaves
(Lycopersicon esculentum)• Tomato whole residue
(leaves+stem+part of roots)�Greenhouse trial with lettuce
�Questionnaire surveys �Loosely- and semi-
structured interviews�Direct observation�Review of secondary
sources
Figure 1. Nitrogen release in solution during 21 days (n=3)
• The use of organic extracts to be used as a quick-acting fertilizer is a very relevant option for resource-poor vegetable producers in Cambodia
• The main perceived advantages by farmers of the use of organic extracts are acceleration of crop growth, easy production and use, availability at almost zero cost. Socio-cultural factors also have an influence (environmental and health awareness)
• Diverse means of preparation: materials are chosen in accordance with availability while preparation time and application methods vary
Table 1. Nitrogen recovery in extract solutions
21.649.715.443.431.017.6Tomato plant
21.061.515.034.224.411.8Tomato leaves
6.526.08.125.031.210.1Cabbage leaves
Obtainable with 1 t of fresh
material* (kg N)% of total soluble N
% of total plant N added
Obtainable with 1 t of fresh
material* (kg N)
% of total plant N added
C:N ratioMaterial
Mineral NTotal soluble N
Figure 3. Effect of salinity on lettuce growth
Figure 5. Materials used to prepare
liquid compost
Figure 4. Reasons for the use of
liquid compost
Figure 6. Soaking period of organic
materials before use as liquid compost
25%
62%
13% 7-10 days
10-21 days
more than 21 days
* Assuming a relative water content of 92% for cabbage leaves, and 86% for tomato leaves and tomato plant
The participation of the main author to Tropentag 2009 has been supported by a NATURA travel grant
Acknowledgments
Plant materials released N to solutions at different rates, particularly regarding the mineral N fraction of soluble N.
Ammonium (NH4+) was
the dominant form of
0 5 10 15 20
0
10
20
30
40
Time (days after preparation)
0 5 10 15 20
N in
sol
utio
n (%
of
tota
l N a
dded
)
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NH4+
NO3-
Cabbage Tomato leaves Tomato plant
In Cambodia organic extracts are called ”liquid compost”. About 50% of
the total respondents use this type of fertilizer in addition to other fertilizers.
Most farmers observe that the application of these extracts results in higher and better quality production.
in the farm or in its vicinity and they are both animal and plant derived. Preparation time is about 2-3 weeks. Extracts are always diluted 10-40 times.
Application is either foliar or as a soil drench. The materials used are collected
Number of users (%)
0 20 40 60 80 100
Animal manure
Chromolaena odorata
Urine (animal)
Urine (human)
Leaves from legumes
Kitchen waste
Neem
Crop residues
Chemical fertilizer
Other
Number of users (%)
0 20 40 60 80 100
Health concern
Faster growth
Better quality
Economy
Pest control
Other
Figure 2. Mineral nitrogen, phosphorus and potassium content in extract solutions used for lettuce (n=3)
The extracts contained high levels
of salts, especially Sodium and
Chlorine, resulting in high salinity stress in
lettuce plants after application.
time (days after preparation)
0 10 20 30
Con
cent
ratio
n in
sol
utio
n (m
g l
-1)
50
100
150
200
Cabbage 50 g DM l-1
Tomato leaves 50 g DM l-1
Cabbage 100 g DM l-1
Tomato leaves 100 g DM l-1
Mineral control
Mineral N
0 10 20 30
20
40
60
0 10 20 30
200
400
600
800
Phosphorus Potassium
mineral N in the extracts, while nitrate (NO3
-) tended to disappear from the system.
Extracts contained other nutrients in high concentrations,
often much higher than the mineral control (a mineral
fertigation solution), except for phosphorus.
• Total N recovery in extracts from crop residues was 24-31% of total plant N added
• The mineral N fraction was dominated by ammonium• The concentration of most macronutrients was high compared to a
commercial fertigation solution, except for phosphorus• Extracts contained high amounts of salts, provoking salinity stress in plants